The field of the invention is programmable controllers and more particularly, means for monitoring the various elements thereof to detect and indicate any malfunctions which may occur while the system is operating.
As disclosed in copending U.S. patent application Ser. No. 779,916 entitled "Malfunction Detection System for a Programmable Controller," numerous means are known in the art for the on line detection and indication of malfunctions in relatively small hardwired programmable controllers. Also, elaborate means for accomplishing the same functions in relatively large programmable controllers are well known as disclosed in U.S. Pat. No. 3,997,879 entitled "Fault Processor for Programmable Controller with Remote I/O Interface Racks." Filed on even date herewith is U.S. patent application Ser. No. 790,251 entitled "Programmable Controller with Integral Microprocessor" which discloses a new programmable controller architecture. This programmable controller employs both a microprocessor and a hardwired Boolean processor to control operating devices which connect to the circuits in one or more I/O interface racks. This new architecture requires unique means for monitoring the operation of its elements.